The present invention relates in general to cleaning semiconductor equipment; and more particularly, to a method and system for in-situ cleaning of semiconductor manufacturing equipment, such as silicon dioxide deposition chambers, using a two step, combination of chemistries.
Semiconductor manufacturing equipment is widely employed to fabricate electronic devices and integrated circuits on substrates or wafers. Many different types of semiconductor equipment are used in the fabrication process, such as for example: heat treatment chambers used for thermal annealing, oxidation, nitridation and the like, and chemical vapor deposition (CVD) chambers used to deposit thin films. In particular, deposition of thin films of doped and undoped silicon oxide (SiOx), also called silicate glass (SG), find wide application in the production of electronic devices. The chamber used to deposit these films often uses thermally driven chemical reactions. CVD chambers, and associated equipment components such as injectors and the like, used to deposit undoped SiOx films (USG), and doped SiOx films with boron (B) and phosphorous (P) such as BySiOx (BSG), PzSiOx (PSG), and ByPzSiOx (BPSG) often become fouled with solid silicate byproducts of the deposition process. If sufficient solid byproducts build up on the internal surfaces of the chamber, these by products can flake, or spall, from the chamber surfaces and contaminate the substrate or wafer with detrimental particulate solids. The spalling byproduct deposits often land on a wafer-in-process resulting in particle contamination of the integrated circuits. To avoid this particulate contamination the chamber interior and associated equipment components must be periodically cleaned.
Various cleaning techniques have been employed in the art. Manual cleaning of the chambers, and associated equipment components, has been used; however this technique is undesirable due to high labor costs and downtime.
Another technique used in the art is a one step in-situ process, such as that described in U.S. Pat. No. 5,788,778. As described in the ""778 patent, a precursor gas is activated in a remote chamber via a high power source to form a reactive species which is then flowed into the deposition chamber to clean the inside of the deposition chamber. While this technique provides advantages over the manual method, it also has limitations. For example, cleaning rates are still relatively low which results in significant downtime, with the corresponding reduction in product throughput. Further, the cost of the chemicals are high. For example, in the ""778 patent, NF3 may be used in a high power generator to create reactive species for the complete cleaning process, which is very costly. Thus it is desirable to provide an improved method and system for cleaning the chambers.
Accordingly, it is an object of the present invention to provide an improved method and system for cleaning of semiconductor manufacturing equipment.
More particularly, it is an object of the present invention to provide a method and system for in-situ cleaning of semiconductor manufacturing equipment using a combination of a two step process which uses chemicals that selectively target the different types of solid deposits that build up on the chamber and equipment.
For example, in one embodiment, the invention provides a method and system for in-situ, chemical-etch cleaning of chambers and associated equipment components, by using a combination of anhydrous Hydrogen Fluoride (aHF) and atomic Fluorine (atomic-F) in a two step process. The inventors have discovered that the effectiveness of these two different fluorine chemistries vary with the nature of the type of solid deposits, which are either powdery, or dense and film-like, or a combination of both. The inventors have found that aHF quickly and inexpensively removes powdery deposits, while atomic-F quickly and inexpensively removes dense film-like deposits. Other fluorine containing chemicals may be used as described below. The present invention selectively targets the chemicals for cleaning of the deposits for which the individual chemical is most capable; yielding an overall more effective combined cleaning method. This improved method and system of cleaning reduces the chemical cost, and reduces the downtime of the equipment. The use of the two step, combination, inventive method of cleaning chemistries that are selectively targeted to remove different types of deposits offers significant cost and thoroughness benefits over chamber cleaning with one step use of the chemicals individually as in the prior art.